Transfer printing, which originated in the sixties, has been employed industrially only in a limited number of materials: polyester, acrylic, triacetate, polyamide, i.e. in articles made of synthetic fibers. This limitation is due to the very principle on which transfer printing is based, namely the migration in the fiber of dyes which were sublimated during a thermal treatment of the order of 200.degree. C. Fibers which ere not capable of being dyed with dispersed dyes or those which do not withstand the corresponding temperature, are therefore excluded. Consequently, natural fibers and in particular cellulosic fibers are not concerned by this technique, which is preferably applied to polyester.
However, transfer printing presents undeniable advantages: no consumption of water, no pollution, low investment and little space required for the printing proper, very considerable versatility of use since, on the one hand, the same transfer paper allows printing of articles of different textures and, on the other hand, the transfer paper can be stored and printing effected as required.
Document JP 77/38077 discloses a process of transfer printing of wool, cotton or wool-polyester blend fabrics, which consists in effecting a pre-treatment of the fabric to be printed by transfer, such pre-treatment consisting in an impregnation of the fabric with an aqueous dispersion of polyurethane. The transfer paper, comprising an ink containing a sublimable dye, is applied by pressure against the treated fabric at 200.degree. then steamed for 20 minutes at 100.degree. C. The printed fabric obtained has shrink-resistant properties and may be used for golf wear.
Such a known process, despite all the interest that it presents, has, to Applicants' knowledge, not had real industrial applications. From the findings that they have made, Applicants consider that the pretreatment of polyurethane which is proposed in this document is not entirely satisfactory, insofar as the printed articles thus produced do not present the fastness usually required, for all types of colours. In fact, it will be readily appreciated that printed fabrics usually comprise on the same article a large number of colours and that it is important that all the dyes used for printing have an acceptable behaviour, such that there is no running when the article is used and in particular when it is washed.
It is an object of the present invention to propose a process which overcomes the major drawback of transfer printing, namely its limitation to a few synthetic fibers, and also the drawback set forth above of the process employing a prior treatment by impregnation of polyurethane, namely the running of the colours.